In glassware manufacturing, so-called I.S. forming machines are used, which comprise a number of side by side forming sections, each for producing a succession of glass articles.
Each forming section comprises one or more rough molds and one or more finish molds, each of which comprises two half-molds movable with respect to each other between a closed position defining respective molding cavities, and an open position in which to remove the molded article.
The molds are selected according to the type of article for manufacture, and must therefore be changed at each production change, or whenever they fail to ensure the desired surface and/or dimensional quality of the product.
Changing the molds is a time-consuming job that calls for considerable physical strength. Besides having to handle heavy parts that are awkward to grip (some molds can weigh as much as sixty-seventy kilograms), workers are also forced to work in extremely unfavourable conditions, i.e. to remove and replace molds in areas some distance from the edge of the machine bed and to which access is also hampered by other component parts of the machine.
One known solution to the problem is to use lever-operated devices or controlled-axis, e.g. anthropomorphic, manipulators floor-mounted alongside the machine.
This solution makes the molds easier to change, but increases the necessary floor space, by requiring aisles and safety operating areas for the manipulators, and also greatly increases the cost of the machine, so much so that operators continue to opt for manual mold changing solutions.
This is mainly due to the manipulators having to be stable with respect to the structure of the machine, and extremely rigid to handle heavy overhanging weights, to move them along complex, strictly defined trajectories, and to deposit them in strictly defined positions. As a result, manipulators are invariably heavy, bulky, complicated in design, and extremely expensive. By way of example, an anthropomorphic manipulator with a reach of roughly 2000 millimetres weighs roughly fifteen times the load it moves.